A common construction of heavy duty trailers involves an elongate flat bed deck supported on wheels in a suitable manner for rolling movement in a forward direction of a towing vehicle. A hitch connector at a forward end of the trailer secures the trailer to the towing vehicle. Ramps are typically pivotally coupled at a rear end of the trailer for loading objects onto the trailer deck surface. Typically there are two ramps spaced apart at an adjustable lateral spacing for accommodating the various wheel spacings of vehicles to be loaded onto the trailer deck surface. The ramps are typically hinged and rotate between a transport position carried on the bed of the trailer and a loading position in which the ramps provide a declining extension of the bed surface of the trailer extending from the rear of the trailer to the ground. Both the frame of the trailer and of the ramps must be designed to carry a substantial amount of weight during loading and unloading operations and for carrying various objects and vehicles on the trailer, so that the resulting frames of the ramps may be quite heavy, for example being between 100 and 150 pounds for each section of the ramp. It is common for multiple users to be required for manually lifting the ramps and rotating them through approximately 180 degrees of rotation between the loading position and the transport position even when the ramps are provided in plural sections.
Various prior art designs incorporate springs at the hinge coupling the ramps to the deck frame however the biasing provided by conventional spring designs typically limit the amount of weight to be carried so that even when forming the ramps in individual sections to reduce the weight thereof, a considerable weight remains to be manually lifted. Furthermore forming the ramps as separate spaced apart sections is somewhat undesirable as there is a danger of a vehicle slipping off the sides of the narrow individual ramp sections during a loading or unloading operation.